A parliamentary inquiry into the proposed Murray-Darling Basin Plan wants a better explanation of how the Government intends to return water to the river system.

The inquiry says the Government has outlined how much water it wants to return but has so far failed to say where it will get about half of it.

Irrigators have welcomed the inquiry's findings and they agree that Parliament should not consider legislation on the issue without more detail.

But one group of environmental scientists says the inquiry failed to address a much bigger issue.

The head of the inquiry, independent MP Tony Windsor, says water policy is incredibly complicated and at the moment the Murray-Darling Basin Plan does not do much to take the mystery out of it.

"A lot of the planning documentation is based on modelling and a lot of that modelling is not easily explained to the community," he said.

"So we're arguing that one of the key things that the Government and the Murray-Darling Basin Authority should do is make it very clear how they intend or would prefer to put together their water recovery plan so that not only is it feasible for that water to be delivered to some of the environmental icon sites and some of the productive uses, but the community actually understands how that water would be delivered."

Under the plan, 2,750 gigalitres should be returned to the Murray-Darling Basin.

The National Irrigators Council has backed the inquiry's findings, but spokesman Tom Chesson says it is not clear where at least 1,000 gigalitres of that water will come from.

"Is it coming from Victoria, New South, South Australia and which valleys is it coming from?" he said.

"Potentially you know that could wipe valleys out if a good proportion of that was to come from one individual valley.

"So I think that is a good recommendation. My understanding is that that also means how do they make that recovery? Is it through buy backs? Is it through improvements in the way the river operates? Is it in infrastructure?"

Water savings

It wants the Government to release a water recovery strategy and its proposal for environmental water trading before it introduces a plan to Parliament.

Mr Windsor also wants a mechanism that will automatically take into account water savings.

"When savings are made that if there's a target, say in the case 2,750 gigalitres is the target," he said.

"But if there are environmental works and measure efficiencies make that that figure automatically drop, that's what's called a sustainable diversion limit."

Opposition spokesman Simon Birmingham agrees there is a great deal of community concern over what the Murray-Darling Basin plan will mean.

He says at least some of those worries could be addressed with more information.

"The problem to date is that all the focus has been on planning on how much water needs to be recovered and none of it from the Government has been on planning how that water will be recovered," he said.

"If they actually do both things at once then there's a far greater chance of enjoying community support and being able to get cross party support for this plan when it reaches the Parliament."

Exploring all options

Tim Stubbs, an environmental engineer with the Wentworth Group of Concerned Scientists, is less than impressed.

"We've never had a more educated Parliament and that inquiry didn't give that impression. It appeared that people were really there just to get a quote for their local newspaper and push their barrow forward," he said.

"It didn't appear to be trying to address the big issues of the Murray Darling and how we need to tackle this problem."

He says the inquiry should be considering returning more water to the river system.

"The Authority has failed to provide information to anyone on what volume of water we actually need for a healthy river system," he said.

"It's given a volume but that volume is highly adjusted for constraints that are believed to be in the system.

"And a range of them are legal and rules-based constraints. So we don't actually know from the Authority, or anyone, what the scientific value is that we need for a healthy Murray-Darling system.

"Now there's other work that indicates that that's around 4,000 gigalitres. The Murray-Darling Basin Authority have only really looked at the number of 2,750 gigalitres.

"His inquiry was the prime opportunity to take that up and really look into what is the difference and what volumes do we need for a healthy river. It hasn't done that."

Environment Minister Tony Burke is yet to say if the Government will agree to the inquiry's findings.